1. Field of the Invention
This invention relates to a flexible thermoplastic container in which the side walls are squeezed to dispense contents of the container. More particularly, it relates to such squeeze containers in which a flexible tubular body and bottom cover are separately molded and then joined together. The invention is particularly concerned with the hermetically sealing the bottom cover to the tubular body.
2. Background Information
Thermoplastic squeeze containers are typically injection blow molded with the bottom wall integral with the side wall, and are filled through a neck which is often then provided with a dispensing fitment. In some applications, it is not possible to blow mold the container with an integral bottom or it is desirable to have a large bottom opening through which the tubular body can be rapidly filled or through which a mixing ball can be inserted. For instance, it is not possible to injection blow mold a squeeze container with multiple compartments. The tubular body with the appropriate divider(s) and the bottom cover are separately injection molded and then must be assembled.
A major problem in joining a separately molded bottom cover to the flexible tubular wall of a squeeze container is obtaining and maintaining a hermetic seal. The repeated flexure of the tubular body to dispense the contents of the container applies continual stresses which can fatigue the joint between the flexible side wall and the bottom cover.
It is known to sonically weld components of thermoplastic containers. Sonic energy directors in the form of sharp edged projections are used to concentrate the sonic energy to achieve the energy density needed to melt the thermoplastic at the joining surfaces. Without the sonic energy directors, the energy is distributed over too large a surface to achieve the heat needed to fuse the parts. Usually, sonic welding is used for joints in thermoplastic containers which are not subjected to high stress concentrations or, they are used for tacking parts together which are intended to be broken loose during use such as tamper evident closures.
There remains a need for a thermoplastic squeeze container having a separately molded bottom cover which is firmly secured to the flexible tubular body to form a hermetic seal which is maintained throughout the useful life of the container.